A railway vehicle typically has axles mounted in pairs in the form of a truck at each end of the railway vehicle. These trucks typically pivot about a vertical axis of the truck intermediate the two axles and relative to the vehicle body. When the vehicle traverses a curve, the vehicle chords across the curve from truck axis to truck axis. If the wheels are not radially aligned on a curve, then the wheels are subject to increased noise and wear. Many mechanisms have been developed to steer such axles to a radial alignment.
Typically the wheels and axle of a railway truck are of unitary construction called a wheelset and the axil is mounted in bearings toward either end. A problem of steering the axles of a railway truck s to provide for transfer of support load from the axle bearing housing into the railway vehicle structure without constraining the horizontal motions required for steering.
Some prior designs have unutilized sliding elements or elastic members which shear in the horizontal plane to allow steering motions of the axles. These designs have the disadvantages that they introduce forces into the steering mechanism and are subject to wear. Canadian Patent No. 1,083,886 overcomes this problem by providing for horizontal motions through a pivoted element. A drawback to this design is that if it is desired to provide substantial vertical motion, the design becomes quite complicated by the addition of the required springs and guides.
U.S. Pat. No. 4,170,179 to Vogel describes a steering apparatus for rail vehicles utilizing two pairs of guide rods which pivotally attach to the bearing housings at diametrically opposed points. In Vogel, a pair of springs extends between the bearing housings and the railway truck frame. In Vogel, one of the guide rods extends between the truck frame and a first pivotal connection on the bearing housing. The other guide rod connects the bearing housing to the vehicle body either directly or through an intermediate linkage. Relative longitudinal movement between the truck frame and the vehicle body is transmitted to the bearing housing through the latter guide rod. This longitudinal movement causes rotation of the bearing housing about the first pivotal connection, which results in longitudinal movement of the end of the wheelset mounted therein.
In the illustrations in Vogel, the first pivotal connection is shown as being beneath the outer spring of the pair of support springs rather than above the center line of the wheelset. Rotation of the bearing housing will therefore result in raising or lowering of the bearing housing depending on the direction of rotation. As both ends of a given wheelset are moved in opposite directions by the steering mechanism, steering input into the device of Vogel will cause one end of the wheelset to be raised relative to the truck frame and the other to be lowered.
Another drawback to the structure of Vogel is that it does not balance the weight of the railway vehicle against the forces generated by steering input to reduce the amount of steering force required and backlash generated.